Long-term use

"I have been using Dr Michaels Cream for two years already. So far I am absolutely happy, but I would like to know if there have been any long term tests done "the loss of effect if used long term". I am very surprised that it still "works" like at the beginning. That is why I would also like to know if there is any product for "change" of the treatment? The idea that after certain amount of time I would again have to look for a product that works truly terrifies me" :-(

Lenka Mandikova